Showing papers by "International Maize and Wheat Improvement Center published in 1988"
100 citations
TL;DR: Byerlee and Tripp as mentioned in this paper argued that the farming systems perspective in agricultural research should be seen as performing an integrative role in research systems, and that the desarrollo of this orientation ayuda a reforzar los vinculos dentro de los sistemas nacionales de investigacion entre los programas de productos and entre disciplinas for la investigacion tanto aplicada como adaptiva.
Abstract: SUMMARY The principal contribution that the farming systems perspective brings to agricultural research is a farmer and problem-solving orientation. Development of this orientation helps strengthen linkages in national research systems between commodity programmes and between disciplines for both applied and adaptive research. It can also strengthen linkages between research and extension and between research and policy analysis. Issues in strengthening each of these linkages are briefly reviewed with particular emphasis on the socio-economic dimensions and the potential role of social scientists. It is argued that the farming systems perspective in agricultural research should be seen as performing an integrative role in research systems. This can often be developed without significant institutional reorganization. Derek Byerlee y Robert Tripp: Reforzando vinculos en la investigation agricola a traves de una perspectiva de sistemas agricolas: Lafuncionde los cientificos sociales. RESUMEN El principal aporte que trae la perspectiva de los sistemas agricolas a la investigacion agricola es una oricntacion hacia el cultivador y la resolucion de problemas. El desarrollo de esta orientation ayuda a reforzar los vinculos dentro de los sistemas nacionales de investigacion entre los programas de productos y entre disciplinas para la investigacion tanto aplicada como adaptiva. Tambien puede reforzar vinculos entre la investigacion y la extension y entre la investigacion y el analisis de politicas. Se repasan brevemente los temas en el refuerzo de cada uno de estos vinculos, con enfasis especial en las dimensiones socioeconomicas y la posible funcion de los cientificos sociales. Se argumenta que la perspectiva de los sistemas agricolas en la investigacion agricola deben verse como cumpliendo un papel de integration en los sistemas de investigacion. Esto a menudo puede ser desarrollado sin una gran reorganization institucional.
29 citations
TL;DR: A spatial method with a modified conventional regression analysis method was compared to determine the yield stability of 27 CIMMYT maize varieties evaluated at 37 locations and was considered the more useful of the two methods.
Abstract: A major objective of the CIMMYT Maize Program is to develop open-pollinated varieties of maize (Zea mays L.) that are well adapted to a wide range of environments. To achieve this breeding goal, it is essential that the program use a stability technique that will identify high-yielding, stable genotypes accurately in international trials conducted under different environmental conditions. The objective of this study was to compare a spatial method with a modified conventional regression analysis method to determine the yield stability of 27 CIMMYT maize varieties evaluated at 37 locations. The methods also were compared on the basis of their consistency in assessing the stability of varieties when certain locations were omitted, and when subsets of varieties were analyzed. The varieties found to be stable by the spatial method with all sites included in the analysis were also stable (1) when the lowest and highest yielding sites were excluded from the analyses, and (2) when the varieties were considered, along with others, as a subset of the original group of materials. Stability parameters determined by regression analysis, however, varied for some varieties when (1) extreme sites were excluded, and (2) a subset of entries was considered in isolation. Because the spatial method was more consistent in identifying high-yielding stable varieties, it was considered the more useful of the two methods.
26 citations
21 citations
TL;DR: General combining ability was the major component of variation, although specific combining ability (SCA) was present in most cases, and suggests that isolates vary in aggressiveness rather than in virulence.
Abstract: All crosses, except for reciprocals, were made among ten cultivars originating from crop improvement programs in North Africa and the Middle East. The entries varied widely in reaction to Septoria tritici. F1 and F2 progenies of the crosses were evaluated using eight S. tritici isolates from seven countries in the Mediterranean area. Thus, sixteen separate combining ability analyses were excecuted. General combining ability (GCA) was the major component of variation, although specific combining ability (SCA) was present in most cases. Additive variance thus appears to be of predominant importance. Nevertheless, non-additive variance may interfere when line selection in a breeding program is practiced. While differing greatly among cultivars, specific GCA effects for each cultivar separately were of similar magnitude for all isolates. Ranking statistics determined that cultivars were ranked in similar order for both means and specific GCA effects independent of the isolate used. Different isolates may therefore interact with similar or identical genetically controlled mechanisms in a particular cultivar. This could indicate the absence of differential gene-for-gene relationships and suggests that isolates vary in aggressiveness rather than in virulence.
16 citations
TL;DR: E Evaluation of the yield stability of a group of CIMMYT tropical maize populations across international environments, measured by the performance of varieties derived from them, showed that the populations Mezcla Tropical Blanca, La Posta and Amarillo Dentado produced the most stable varieties across environments.
Abstract: SUMMARY Evaluation of the yield stability of a group of CIMMYT tropical maize populations across international environments, measured by the performance of varieties derived from them, showed that the populations Mezcla Tropical Blanca, La Posta and Amarillo Dentado produced the most stable varieties across environments. Mezcla Tropical Blanco and Amarillo Dentado produced selections with good stability in both low and high yielding environments while La Posta produced varieties with better performance in favourable environments. 'Acrosssite' varieties were not consistently more effective than 'site-specific' varieties in improving yield stability. Varieties selected for some specific population-environment combinations have been very stable in other areas of the world. J. Crossa, B. Westcott y G Gonzalez: Estabilidad de rendimiento de genotipos de maiz en distintos medios ambientes internacionales: Maiz tropical de plena estacion.
15 citations
TL;DR: Results of the stability analyses indicated that selections from Mezcla Amarilla exhibited good stability in high yielding sites, and varieties derived from Antigua-Republica Dominicana tended to be more stable in unfavourable environments.
Abstract: The yield stability of some CIMMYT tropical maize (Zea mays L.) populations of early and intermediate maturity, measured by the performance of varieties derived from them, was determined. Results of the stability analyses, conducted over international environments from 1980 to 1983, indicated that selections from Mezcla Amarilla exhibited good stability in high yielding sites. Varieties derived from Antigua-Republica Dominicana tended to be more stable in unfavourable environments, whereas selections from Blanco Cristalino-1 and Blanco Dentado-2 were stable in both low and high production sites. The combination of enviromental factors in the specific test locations, namely Poza Rica (Mexico), Tocumen (Panama), Islamabad (Pakistan), and Ferkessedougou (Ivory Coast), allowed selection of varieties that are very stable in other regions of the world. The varieties formed on the basis of multilocational data do not seem to be any more stable than those formed using data from a single location.
10 citations
TL;DR: In this article, the first empirical data collected on parallel channel rice marketing activities, suggests that excessive reliance on either the state or the private sector is likely to result in unsatisfactory performance.
8 citations
TL;DR: The length of time from promycelium emergence to secondary sporidia production of Tilletia indica varies considerably, and this may be a safety mechanism by which the fungus ensures that there are sporidia for dispersal, as soon as optimum temperature and moisture conditions are available.
Abstract: The length of time from promycelium emergence to secondary sporidia production of Tilletia indica varies considerably This may be a safety mechanism by which the fungus ensures that there are sporidia for dispersal, as soon as optimum temperature and moisture conditions are available Alternatively, in the field there is a factor that triggers teliospore germination and secondary sporidia production to coincide with the heading stage of the wheat crop Occasionally two or even three promycelia arise from the same teliospore, with each one capable of bearing primary sporidia
8 citations
Journal Article•
TL;DR: It is sought to verify if it is possible to obtain hybrids able to tolerate the acidity of the soil, through the mixing of A-lines susceptible with R-lines tolerance, which will make easier the seed production on fertil soils.
Abstract: Exist in the world, millions of acres of unexploited soil, due to the grade of acidity of the soil, and with aluminum and manganese at toxic levels. There is a practical and rational alternative; it would be the obtaining of improved materials, using parentals able to tolerate the acidity. We seek to verify if it is possible to obtain hybrids able to tolerate the acidity of the soil, through the mixing of A-lines susceptible with R-lines tolerance, wich will make easier the seed production on fertil soils. The hybrids resulting of the cross of two A-lines and nine R-line were evaluated. One of the best combination was 8-Yellow-PI x MN-4508 (4548 kg/ha). All the hybrids that involve the line 8-Yellow-PI were better in all the combinations both in acid and productive soils.
1 citations